Vacuum chambers for degasifying metal melts



April 1967 H. KNUPPEL ETAL VACUUM CHAMBERS FOR DEGASIFYING METAL MELTS Filed Oct. 50, 1962 .rllnlllllll lllllfilililtl 'IIIIIIIIIIIIIIIIIIIIIII P Mn 0: e v.3: +4- a I H United States Patent 6 Claims. 61. 266-34) In one method of degasifying molten metals which is used especially for iron and its alloys, a part of the metal melt in the form of a ladle, through an inlet and outlet pipe a refractory lining and jacket, into a vacuum chamber where it is degasified, and is then returned to the ladle through the same pipe. The vacuum chamber is periodically filled and emptied by variation of the distance between the vacuum chamber and the ladle.

In the apparatus for carrying out this method, a tapering metal cap (which is usually conical) is pushed onto the bottom end of the connecting pipe before it is moved downwards into the melt in the ladle. The fusible cap is intended to prevent slag from entering the inlet and outlet pipe and thence the vacuum chamber as the end of the pipe passes through the layer of slag floating on the metal melt. As the cap enters the molten metal below, the cap melts and opens the pipe to allow the metal to flow up it.

It has been found that a cap which is only pushed on to the pipe over the end of the refractory jacket does not sufliciently reliably prevent slag from entering the pipe and the vacuum chamber, because the refractory jacket on the pipe ultimately wears out and its surface does not remain sufiiciently smooth to prevent gaps from forming for the passage of slag between the jacket and the flanged edge of the cap which fits around it.

The present invention aims at overcoming the leakage of slag into the pipe and to this end, according to the present invention, the metal cap is attached to the end face of the pipe and a packing which seals the joint against the entry of molten slag and which preferably consists of fibrous material, for example mineral or steel wool, is provided between the cap and the end face of the pipe. Any gaps which may occur between the cap and the jacket are thus reliably closed. If the refractory lining of the connecting pipe consists of magnesite, it has been found advantageous to use a loW-lime-content mineral wool or steel wool as packing material.

The conical cap connected to the end of the connecting pipe can be made particularly effective in preventing slag from penetrating into the pipe and the vacuum chamber by providing the outer surface of the cap with a covering of cardboard and a wooden plug inserted in an opening in the apex of the conical ca The effect of this covering and plug is to prevent any deposition of a slag crust on the metal surface of the cap, since if such a crust is later melted by the molten metal it runs into the connecting pipe. The plug also ensures that after the piercing of the top of the slag, the protective cap first melts at the apex of the cone as it penetrates into the molten metal. To protect the cardboard covering and the wooden plug from burning before the immersion of the connecting pipe, their surfaces may be painted with, for example, aluminum bronze and the interior of the cap may be given a lining of mineral wool.

An example of the previous type of cap used and some examples of the present invention are illustrated diagrammatically in the accompanying drawings in which:

FIGURE 1 is a vertical section through the usual apparatus for the degasification of metal melts; and

Claims FIGURES 2 to 6 are vertical sections through the bot tom of the pipe showing five different examples of caps.

As shown in FIGURE 1, a cap 2 is simply pushed over the jacket on a pipe 1 extending downwards from a vacuum chamber. The cap is shown penetrating into a molten slag layer 3 on a metal melt 5 in a ladle 4.

In the example of the invention shown in FIGURE 2, the cap 2 is attached to the end face 6 of the pipe jacket by means of holders 8 made of wire and eyes 7 welded to the connecting pipe 1'. Three holders 8 distributed around the periphery of the connecting pipe are generally suiiicient for adequate fastening.

An annular space 9 formed between the end face 6 of the jacket and the end faces of the pipe 1' and its lining and the cap 2 is filled with packing 9' of mineral wool.

In FIGURES 3 and 4 caps 2 are shown, the maximum diameters of which are smaller than the outer diameter of the end face 6 of the refractory jacket of the connecting pipe 1. In these examples the packings 9 are held by an annular disc 10 (FIG. 3) which is parallel to the end face 6 and is connected to the conical cap. The tube 11 is coaxial with the connecting pipe 1. As shown in FIGURE 5, the tube 11 is of such a length that the distance between its end 12 and the apex 13 of the cap 2 is greater than the thickness of the layer of slag 3 in the ladle 4. If the lining of the connecting pipe is sufficiently true to size and resistant to wear, the tube 11 can be used directly as an attachment for the conical cap.

As shown in FIGURE 6, the cap 2 may be provided with a covering 14 which evolves a gas on immersion in the layer of slag and this produces a turbulence diverting the slag away from the pipe. In this example the covering is of 2 to 3 mm. thick cardboard. Further a wooden plug 15 is inserted into an opening in the apex of the cone. The covering has an external coat of protective aluminum bronze paint and the interior of the conical cap is provided with a layer 16 of mineral wool.

We claim:

1. In an apparatus for gasifying molten metals and including a vacuum chamber having a downwardly extending open-end inlet and outlet pipe connected to the bottom of said chamber and adapted to dip with its open end into a container holding a melt of a metal to be degassed under a slag layer, said pipe having a refractory jacket and a generally conical downwardly tapering metal cap attached to the end face of said pipe and a packing between said jacket and said cap sealing said jacket and said cap against the entry of slag into said pipe, the improvement which comprises an upright tube fixed at its lower end to the inner face of said cap and extending co-axially from said cap upwardly within said pipe to a distance such that the distance between its upper end and the apex of said cap is greater than the thickness of the layer of slag upon said metal in said container, said tube, said cap and said end face defining the space containing said packing.

2. The improvement defined in claim 1 wherein said cap has an opening at said apex, further comprising a wooden plug received in said opening which burns upon immersion of said pipe in said melt through said layer of slag whereby the gases released upon burning of said plug rise along said cap and prevent the accumulation of slag thereon and on said pipe.

3. The improvement defined in claim 2, further comprising a cardboard cover overlying the outer surface of said cap for decomposition by said slag layer upon immersion of said pipe in said melt.

4. An apparatus for the degassing of a metal melt overlain by a layer of slag, comprising a vertically displaceable vacuum vessel having a depending conduit communicating with its interior for the alternate introduction and discharge of metal from said melt into said vessel upon the lowering and raising thereof; a container for said melt below said'vessel, said conduit having a refractory sleeve formed at its lower extremity with an end face generally perpendicular to said conduit; a downwardly tapering, generally conical protective cap having its base abutting said end face in all-around contact therewith and terminating at said end face; retaining means for holding said cap against said end face; and an annular mass of relatively heat-resistant fibrous material surrounding the interior of said sleeve and circumferentially disposed between said end face and said cap in the region of abutting contact of the base of said cap and said end face, wherein said retaining means includes an upstanding tubular member affixed to the interior of said cap and generally coaxial therewith and with sa d conduit while extending upwardly into the latter beyond said end face.

5. An apparatus for the degassing of a metal melt overlain by a layer of slag, comprising a vertically displaceable vacuum vessel having a depending conduit communicating with its interior for the alternate introduction and discharge of metal from said melt into said vessel upon the lowering and raising thereof; a container for said melt below said vessel, said conduit having a refractory sleeve formed at its lower extremity with an end face generally perpendicular to said conduit; a downwardly tapering, generally conical protective cap having its base abutting said end face in all-around contact therewith and terminating at said end face; retaining means for holding said cap against said end face; and an annular mass of relatively heat-resistant fibrous material surrounding the interior of said sleeve and circumferentially disposed between said end face and said cap in the region of abutting contact of the base of said cap and said end face, wherein said cap is formed at its apex with a passage, further comprising a wooden plug received in said passage carbonizable upon immersion in said melt through said layer of slag whereby the gases released upon carbonization of said plug rise along said cap and prevent the accumulation of slag thereon and on said pipe.

6. An apparatus for the degassing of a metal melt overlain by a layer of slag, comprising a vertically displaceable vacuum vessel having a depending conduit communicating with its interior for the alternate introduction and discharge of metal from said melt into said vessel upon the lowering and raising thereof; a container for said melt below said vessel, said conduit having a refractory sleeve formed at its lower extremity with an end face generally perpendicular to said conduit; a downwardly tapering, generally conical protective cap having its base abutting said end face in all-around contact therewith and terminating at said end face; retaining means for holding said cap against said end face; and an annular mass of relatively heat-resistant fibrous material surrounding the interior of said sleeve and circumferentially disposed between said end face and said cap in the region of abutting contact of the base of said cap and said end face, further comprising a cardboard cover overlying the outer surface of said cap for decomposition by said slag layer upon immersion of said pipe in said melt.

References Cited by the Examiner UNITED STATES PATENTS 1,750,390 3/1930 Connor 266-34 2,024,132 12/1935 Sander. 2,929,704 3/1960 Harders 266--34 XR JOHN F. CAMPBELL, Primary Examiner.

DEIJBERT E. GANTZ, Examiner.

PAUL M. COHEN, Assistant Examiner. 

1. IN AN APPARATUS FOR GASIFYING MOLTEN METALS AND INCLUDING A VACUUM CHAMBER HAVING A DOWNWARDLY EXTENDING OPEN-END INLET AND OUTLET PIPE CONNECTED TO THE BOTTOM OF SAID CHAMBER AND ADAPTED TO DIP WITH ITS OPEN END INTO A CONTAINER HOLDING A MELT OF A METAL TO BE DEGASSED UNDER A SLAG LAYER, SAID PIPE HAVING A REFRACTORY JACKET AND A GENERALLY CONICAL DOWNWARDLY TAPERING METAL CAP ATTACHED TO THE END FACE OF SAID PIPE AND A PACKING BETWEEN SAID JACKET AND SAID CAP SEALING SAID JACKET AND SAID CAP AGAINST THE ENTRY OF SLAG INTO SAID PIPE, THE IMPROVEMENT WHICH COMPRISES AN UPRIGHT TUBE FIXED AT ITS LOWER END TO THE INNER FACE OF SAID CAP AND EXTENDING CO-AXIALLY FROM SAID CAP UPWARDLY WITHIN SAID PIPE TO A DISTANCE SUCH THAT THE DISTANCE BETWEEN ITS UPPER END AND THE APEX OF SAID CAP IS GREATER THAN THE THICKNESS OF THE LAYER OF SLAG UPON SAID METAL IN SAID CONTAINER, SAID TUBE, SAID CAP AND SAID END FACE DEFINING THE SPACE CONTAINING SAID PACKING. 